A serious discussion took place between P. Curie in Paris and E. Rutherford in Montreal from 1900 until 1904 through the medium of scientific publications. P. and M. Curie had observed that radium produces “induced radioactivity”, whereas, at the same time, Rutherford had observed that thorium emits a kind of “emanation”. P. Curie, performing different experiments with his collaborators, believ...